Probably a silly question, but what would cause the utlity frequency to drop to 59.8 and 59.75 and then return to normal? Called the power company and they said nothing they were doing at this time should affect my frequency. I was only aware of this problem because my large UPS that feeds a data services area was in alarm. Checking my incoming metering on both sides of my main tie main gear I was able to measure and record these anomalies. After about 30 minutes everything returned to normal. During this time voltage remained very consistant at around 482-485 on the incoming meter.
Frequency
- Thread starter caj1962
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charlie
Senior Member
- Location
- Indianapolis
Re: Frequency
It would be a lot of large loads coming on line at the same time or another electric utility having problems and causing the grid to sag. The northeast outage had a little sag for a few days. The Midwest ISO stopped us from being involved in that outage.
It would be a lot of large loads coming on line at the same time or another electric utility having problems and causing the grid to sag. The northeast outage had a little sag for a few days. The Midwest ISO stopped us from being involved in that outage.
- Location
- Illinois
- Occupation
- retired electrician
Re: Frequency
Charlie,
I thought that everything west of the Rockies with the exception of Texas was tied to a common grid and the the frequency in all parts of the grid is the same.
Don
Charlie,
I thought that everything west of the Rockies with the exception of Texas was tied to a common grid and the the frequency in all parts of the grid is the same.
Don
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Frequency
How confident are you in the quality (i.e., precision and accuracy) of your instrument?
How confident are you in the quality (i.e., precision and accuracy) of your instrument?
charlie
Senior Member
- Location
- Indianapolis
Re: Frequency
It is all tied together, that is why we have operators. They are responsible for disconnection if we get into trouble in a local area. If our generators are running slower (or faster) than X% of the fundamental, we will get kicked off the grid to keep us from pulling everyone else down. It just takes a little bit but I don't know the parameters.
Are you sure about Texas? I thought Texas was tied into the grid just like us.
It is all tied together, that is why we have operators. They are responsible for disconnection if we get into trouble in a local area. If our generators are running slower (or faster) than X% of the fundamental, we will get kicked off the grid to keep us from pulling everyone else down. It just takes a little bit but I don't know the parameters.
Are you sure about Texas? I thought Texas was tied into the grid just like us.
- Location
- Illinois
- Occupation
- retired electrician
Re: Frequency
Charlie,
The US Department of Energy says there are three "interconnects" or girds in the lower 48 states. There are some large AC-DC-AC converters used to transfer power between the "interconnects".
I didn't know that they cut part of the grid loose when the frequency drops. I seem to remember reading about a master "clock" on the eastern grid and if it got behind because of low frequency under heavy demand, then they would kick the frequency up a bit when the demand was lower to get the master clock back in sync with the Navel Observatory Atomic clock, but that was a number of years ago when I read the article and I could have the details wrong.
Don
Charlie,
The US Department of Energy says there are three "interconnects" or girds in the lower 48 states. There are some large AC-DC-AC converters used to transfer power between the "interconnects".
I didn't know that they cut part of the grid loose when the frequency drops. I seem to remember reading about a master "clock" on the eastern grid and if it got behind because of low frequency under heavy demand, then they would kick the frequency up a bit when the demand was lower to get the master clock back in sync with the Navel Observatory Atomic clock, but that was a number of years ago when I read the article and I could have the details wrong.
Don
Re: Frequency
I am very confident in my metering equipment, but the big kicker was when I was notified that our UPS was in alarm and by checking it found to be on battery because of the frequency. Every thing was fine about 2 hours ago when I left but it sure is strange. To give a little bit of history to this building service it is a dedicated medium voltage feeder from utilty to a 850,000 foot hospital. This is the first time anything like this has happened since I ahve bben there. 11 years.
If there was a large load shift somewhere on the utilty could this cause the problems I was seeing?
I am very confident in my metering equipment, but the big kicker was when I was notified that our UPS was in alarm and by checking it found to be on battery because of the frequency. Every thing was fine about 2 hours ago when I left but it sure is strange. To give a little bit of history to this building service it is a dedicated medium voltage feeder from utilty to a 850,000 foot hospital. This is the first time anything like this has happened since I ahve bben there. 11 years.
If there was a large load shift somewhere on the utilty could this cause the problems I was seeing?
physis
Senior Member
Re: Frequency
Don and Charlie I used to deal with time equipment that used a synchronous motor whos RPM (1) was dependendant on the AC frequency.
The torque of these things was so ridiculously high in relation to what was required that there was little wear and they would not slow down.
Anyway, if the frequency changed, so would the time. I never checked this out but I was told that there were continual compensations in order to adjust for frequency variations not only over a few cycles but also over hours days or monthes.
Half an eon ago there were synchronous wall clocks everywhere.
Don and Charlie I used to deal with time equipment that used a synchronous motor whos RPM (1) was dependendant on the AC frequency.
The torque of these things was so ridiculously high in relation to what was required that there was little wear and they would not slow down.
Anyway, if the frequency changed, so would the time. I never checked this out but I was told that there were continual compensations in order to adjust for frequency variations not only over a few cycles but also over hours days or monthes.
Half an eon ago there were synchronous wall clocks everywhere.
Re: Frequency
Charlie, I used to work for Public Service Company of Oklahoma (PSO) who was owned by Central and Southwest (CSW)at the time, now AEP. CSW owned West Texas Utilities (WTU), and SWEPCO, both Texas ustilities. PSO used to have interconnects with WTU and SEPCO and we had to interconnect via DC. The conversions all happened in one sub-station yard (AC-DC-
AC like a UPS). The reason is Texas is an island from all grids.
They did this as a result from the blackout in New York back in the 60's from under frequency operation. Just thought you might want to know.
Charlie, I used to work for Public Service Company of Oklahoma (PSO) who was owned by Central and Southwest (CSW)at the time, now AEP. CSW owned West Texas Utilities (WTU), and SWEPCO, both Texas ustilities. PSO used to have interconnects with WTU and SEPCO and we had to interconnect via DC. The conversions all happened in one sub-station yard (AC-DC-
AC like a UPS). The reason is Texas is an island from all grids.
They did this as a result from the blackout in New York back in the 60's from under frequency operation. Just thought you might want to know.
jtester
Senior Member
- Location
- Las Cruces N.M.
Re: Frequency
Charlie and Don
The western states are interconnected, and Texas except for El Paso and other few western areas are connected to a central grid. From there, I don't know. I know of 2 interconnects where AC is converted to DC and then back to AC to deal with the different grids not being synchronized. Public Service of New Mexico has one, and El Paso Electric has another. These allow for the exchange of energy between the western states and the grid that Texas is in.
Jim T
Charlie and Don
The western states are interconnected, and Texas except for El Paso and other few western areas are connected to a central grid. From there, I don't know. I know of 2 interconnects where AC is converted to DC and then back to AC to deal with the different grids not being synchronized. Public Service of New Mexico has one, and El Paso Electric has another. These allow for the exchange of energy between the western states and the grid that Texas is in.
Jim T
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